Methods and apparatus for preventing rainout

ABSTRACT

Components for a respiratory treatment apparatus that is capable of providing a humidified respiratory treatment permit a reduction in condensation in a patient interface and/or its gas delivery tubing. In some embodiments, a rainout valve that may be an integrated component of a humidifier output aperture, or coupled thereto, may reduce condensation with a vapor barrier operable to selectively block and permit humidified gas transfer from the humidifier. For example, the barrier may be operable to open in response to a flow of pressurized breathable gas that may be generated by a flow generator of the respiratory treatment apparatus. In the absence of such a generation of pressurized flow, the barrier may prevent a transfer of the humidified gas such as into a conduit for a patient interface by retracting to a closed position. Example vapor barriers may include a resilient membrane, cover, bellows, flap, shutter or other suitable valve.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/820,620, filed on Mar. 4, 2013, which application is anational phase entry under 35 U.S.C. § 371 of International ApplicationNo. PCT/AU2011/001137, filed Sep. 2, 2011, which claims priority fromAustralian Provisional Patent Application No. 2010903971, filed Sep. 6,2010, all of which are incorporated herein by reference.

FIELD OF THE TECHNOLOGY

The present technology relates to methods and apparatus for preventingcondensation or rainout in conduits or devices attached to all forms ofhumidifier systems, such as a humidified respiratory treatmentapparatus. Such apparatus may provide respiratory pressure treatmentincluding, for example, invasive and non-invasive ventilation,Continuous Positive Airway Pressure (CPAP), Bilevel therapy, high flowtherapy and treatment for sleep disordered breathing (SDB) conditionssuch as Obstructive Sleep Apnea (OSA), and for various other respiratorydisorders and diseases such as respiratory insufficiency, asthma andChronic Obstructive Pulmonary Disease (COPD). Embodiments of thetechnology may help to reduce the rainout in respiratory air deliveryconduits attached to humidifier systems.

BACKGROUND OF THE TECHNOLOGY

Respiratory treatment apparatus commonly include means to alter thehumidity of a provided breathable gas in order to reduce drying of thepatient's airway and consequent patient discomfort and associatedcomplications. The use of a humidifier placed between the flow generatorof such an apparatus and the patient interface, produces humidified gasthat minimizes drying of the nasal mucosa and increases patient airwaycomfort. The humidifier is generally placed between the flow generatorand the air delivery conduit, with the air delivery conduit beingattached to the patient interface unit.

As schematically shown in FIG. 1, a respiratory treatment apparatus, forexample a Continuous Positive Airway Pressure (CPAP) system, generallyincludes a positive airway pressure (PAP) device 2000 with a flowgenerator, a humidifier 2005, an air delivery conduit 2010 (alsoreferred to as a tube or tubing), and a patient interface 2030. The airdelivery conduit 2010 is coupled to the outlet 2012 of the humidifier2005. In use, the respiratory device 2000 generates a supply ofpressurized air that is humidified by the humidifier 2005 and deliveredto the patient via an air delivery conduit 2010 that includes one endcoupled to the outlet 2012 of the humidifier 2005 and an opposite endcoupled to the inlet 2014 of the patient interface 2030. The patientinterface comfortably engages the patient's face and providescommunication with the patient's airways. The patient interface or maskmay have any suitable configuration as is known in the art, e.g.,full-face mask, nasal mask, oro-nasal mask, mouth mask, nasal prongs,etc. Also, headgear may be utilized to comfortably support the patientinterface in a desired position on the patient's face.

Many humidifier types have been proposed, including humidifiers that areeither integrated with or configured to be coupled to the relevantrespiratory treatment apparatus. While passive humidifiers can providesome relief, generally a heated humidifier is required to providesufficient humidity and temperature to the air so that patient will becomfortable.

Humidifiers may typically include a water tub having a capacity ofseveral hundred milliliters, a heating element for heating the water inthe tub, a control to enable the level of humidification to be varied, agas inlet to receive gas from the flow generator, and a gas outletadapted to be connected to a gas conduit that delivers the humidifiedpressurized gas to the patient's interface unit.

Air delivery conduits are generally used to connect a patient interfaceto a respiratory humidifier system to enable delivery of the humidifiedgas flow to the patient. Air delivery conduits are available in avariety of lengths and diameters. For respiratory conduits, a standardtubing may have an external diameter of 22 mm (internal diameter 19 mm)and lengths of 1.8 metres or 2 metres. Smaller conduits or tubingdiameters such as 15 mm tubing may be used as described in co-pendingU.S. application Ser. No. 12/461,967 filed 28 Aug. 2009, the content ofwhich is incorporated herein in its entirety.

Both unheated and heated air delivery conduits are known to be used withCPAP and ventilation systems. The conduits are generally attached to theoutlet of the humidification system at one end and to a patientinterface unit at the opposing end. In such humidification systems acommon problem can occur with rainout within the air delivery conduit.The humidified air may cool on its path along the conduit from thehumidifier to the patient, leading to the phenomenon of “rain-out”, orcondensation, forming on the inside of the conduit. In use, heated airdelivery conduits assist in addressing the issues with rainout orcondensation within the conduit. For example, a heated conduit maymaintain a desired temperature throughout the heated conduit preventingthe cooling of the humidified gas flowing through it during operation ofthe respiratory treatment apparatus.

However, rainout or condensation may also occur when the system isturned off after use when the humidified air remaining within the systembegins to cool. Some systems include or recommend a controlled cool downperiod for the humidifier and/or the heated conduit to assist inreducing the level of rainout. However, some rainout or condensationstill tends to occur within the conduit. The presence of condensation ormoisture within the conduits can lead to bacterial or microbial growthwithin the conduits and hygiene issues.

It may be desirable to develop devices to reduce rainout or condensationwithin conduits attached to humidification systems such as whenhumidification is no longer being provided or when the system is turnedoff.

SUMMARY OF THE TECHNOLOGY

The present technology involves components of a respiratory treatmentapparatus capable of providing a humidified breathable gas.

Some embodiments of the present technology may include a vapor barrierfor a gas channel of the respiratory treatment apparatus.

Still further embodiments may include such a vapor barrier beingoperable to selectively permit and prevent a transfer of humidified gasin the gas channel of the respiratory treatment apparatus.

Some embodiments relate to such a vapor barrier being operable formovement to selectively permit and prevent a transfer of humidified gasin response to the presence or absence of a flow of breathable gasgenerated by the respiratory treatment apparatus.

For example, a device may reduce conduit rainout attributable to abreathable supply of humidified gas by a respiratory treatmentapparatus. The device may include a breathable gas conduit having aninput aperture and an output aperture. The gas conduit is configured asa channel for movement of a humidified gas between the input apertureand the output aperture. The conduit may further include a vapor barrierin the channel between the input aperture and the output aperture of thegas conduit. The vapor barrier may be operable to selectively permit andprevent vapor to pass from the input aperture to the output aperture.

In some such cases, the vapor barrier may be configured to normally sealthe channel to prevent vapor passing from the input aperture to theoutput aperture. Optionally, the vapor barrier may be configured to opento permit vapor to pass from the input aperture to the output apertureby an application of pneumatic pressure applied at the input aperturethat exceeds pressure at the output aperture. Moreover, the vaporbarrier may be configured to close to prevent vapor passing from theoutput aperture to the input aperture with a pneumatic pressure appliedat the output aperture that exceeds or is equal to the pressure at theinput aperture.

In some such embodiments, the vapor barrier may include a valve flap,such as a valve flap formed of a flexibly resilient material.Optionally, the vapor barrier may be formed as a bellows or a duckbillvalve. Still further, the vapor barrier may include an aperture coverand a biasing member or spring.

In some embodiments of such a device, the gas conduit may also includean atmosphere access port. In such a case, the vapor barrier may beconfigured to cover the atmosphere access port when the vapor barrierpermits vapor to pass from the input aperture to the output aperture.Such a vapor barrier may also be configured to uncover the atmosphereaccess port when the vapor barrier prevents vapor passing from the inputaperture to the output aperture.

Optionally, the gas conduit may be configured at the input aperture as acoupling for a humidifier or a humidifier component of a respiratorytreatment apparatus. Alternatively, it may be an integrated component ofa humidifier. Moreover, the gas conduit may be configured at the outputaperture as a coupling for a conduit of a patient interface.

In some embodiments of the present technology, a humidifier includes anoutlet that is adapted to be shut off when no pressurized gas flow istravelling through the humidifier and to the outlet.

Certain embodiments relate to a rainout valve adapted to be coupled toan outlet of a humidifier to block or obstruct the transfer ofhumidified gas from flowing through the valve in the absence of apressurized flow.

Certain embodiments relate to a valve arrangement adapted to adjustablyobstruct an outlet of a humidifier, the valve comprising a first sidecoupled to the humidifier outlet, a second side adapted to couple to aconduit, and a blocking member that is located between the first sideand the second side and is configured to move between a first positionand a second position, wherein in the absence of a force being appliedthrough the valve, the blocking member is in the first position andobstructs access from the first side to the second side, and in thepresence of a force being applied through the valve the blocking memberis adapted to move to a second position to allow access from the firstside to the second side. The force may be a pressurized gas flow. Theblocking member may be a membrane, a flap, such as a silicone flap, aduckbill valve, or any other type of blocking system. Alternatively theblocking member may be moved between the first position and the secondposition by a spring action.

In certain embodiments, the valve arrangement may include asupplementary gas supply port adapted to allow connection of asupplementary gas, such as oxygen, into the second side.

Some embodiments of the valve arrangement may also include an apertureto atmosphere, such as on the second end of the valve. The aperture maybe configured to be open to atmosphere when the blocking member is inthe first position and closed when the blocking member is in the secondposition. The blocking member may be further configured to obstruct theaperture when in the second position.

Some embodiments involve a humidifier including an inlet and an outletand including a valve arrangement coupled to the outlet that is adaptedto adjustably obstruct the outlet of the humidifier in the absence of aforce being applied to the valve. The valve arrangement may beintegrated into the outlet of the humidifier.

Certain embodiments relate to a humidifier having a blocking meanscoupled to the humidifier outlet to prevent humidified gas from leavingthe humidifier when there is no pressurized flow through the humidifier.

Certain embodiments relate to a valve arrangement for controlling theopening and closing of a humidifier outlet.

Certain embodiments relate to a rainout valve adapted to be coupled toan outlet of a humidifier and configured to block the transfer ofhumidified gas from flowing through the valve in the absence of apressurized flow travelling through the humidifier and to the outlet.

Certain embodiments involve a respiratory PAP system. The system mayinclude a flow generator coupled to a humidifier, an air deliveryconduit coupled to an outlet of the humidifier at a first end andcoupled to a patient interface at the opposing end. The humidifieroutlet may include a blocking member to prevent humidified gas fromleaving the humidifier when there is no pressurized flow through thesystem.

Some embodiments relate to a method of controlling rainout in a conduitconnected to a humidifier. The method may involve providing a humidifierhaving an outlet. The outlet may include or be adapted for coupling witha valve arrangement having a movable blocking member. The method mayalso involve providing a conduit adapted to couple with the outlet wherethe humidifier is adapted to provide a supply of humidifier gas to theconduit in use. The method may further include generating a force with acontroller of a flow generator to control the movement of the blockingmember, wherein in the absence of the force the blocking member isconfigured to obstruct the path through the outlet of the humidifier tothe conduit such that no humidified gas may pass through to the conduitand subsequently rainout within the conduit, and in the presence of theforce the blocking member is configured to move to unobstruct the paththrough the outlet of the humidifier to the conduit to allow thehumidified gas to flow through to the conduit. The force may be providedby a pressurized gas flow through the humidifier to the outlet. Thepressurized gas may be provided by the flow generator coupled to thehumidifier.

Certain embodiments relate to a method of preventing rainout in an airdelivery conduit connected to a humidifier, the humidifier including anoutlet that comprises a movable blocking member, wherein in the absenceof pressurized flow through the outlet the blocking member is configuredto block the path through the outlet of the humidifier to the airdelivery conduit and in the presence of pressurized flow the blockingmember is configured to move to unblock the path through the outlet ofthe humidifier to the air delivery conduit to allow the pressurized flowto travel through the air delivery conduit.

Although certain embodiments have been described with respect torespiratory humidification systems it is appreciated that anyhumidification system or vapor transfer system may utilize such ablocking member arrangement to prevent vapor or humidified air to exitthe humidification system or vapor transfer system when not in use, orthere is no flow.

It is noted that there are other types of humidification systems thatrequire the use of conduits to provide or transport the humidified gasto the desired location. Such systems are also encompassed within thescope of the present technology.

Other embodiments, aspects, features, and/or advantages of thistechnology will become apparent from the following detailed descriptionwhen taken in conjunction with the accompanying drawings, which are apart of this disclosure and which illustrate, by way of example,principles of the disclosed technology.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings facilitate an understanding of the variousembodiments disclosed. In such drawings where the same or similarnumbers are used to identify similar components:

FIG. 1 schematically depicts a prior art humidifier respiratory systemconnected to a patient interface;

FIG. 2A schematically depicts an integrated humidifier respiratorysystem connected to a patient interface according to a sample embodimentof the technology;

FIG. 2B schematically depicts a humidifier respiratory system connectedto a patient interface according to another example embodiment of thetechnology;

FIG. 3 schematically depicts a humidifier respiratory system connectedto a nasal cannula according to an example embodiment of the technology;

FIG. 4 is an illustration of a humidifier system according to a furtherexample embodiment of the technology;

FIG. 5 is an illustration of an embodiment of the valve arrangement ofthe system in FIG. 4;

FIGS. 6A and 6B schematically depict a valve arrangement including amembrane mechanism without a flow force and with a flow forcerespectively according to an embodiment of the technology;

FIGS. 7A and 7B schematically depict a valve arrangement including aflap mechanism without a flow force and with a flow force respectivelyaccording to a second sample embodiment of the technology;

FIGS. 8A and 8B schematically depict a valve arrangement including aduckbill mechanism without a flow force present and with a flow forcepresent respectively according to a third example embodiment of thetechnology;

FIGS. 9A and 9B schematically depict a valve arrangement including aspring mechanism without and with the presence of a flow forcerespectively according to a fourth sample embodiment of the technology;

FIGS. 10A and 10B schematically depict a valve arrangement furtherincluding a vent to atmosphere without and with the presence of a flowforce respectively according to a further sample embodiment of thetechnology;

FIG. 11 is an illustration of the outside of a valve arrangement furtherincluding a vent to atmosphere showing the arrangement when there is noflow through the valve from the flow generator;

FIG. 12 is an illustration of the inside view of the valve arrangementof FIG. 11 when there is no flow in the channel of the valve from theflow generator;

FIG. 13 is an illustration of the outside of the valve arrangement inFIG. 11 showing the arrangement when there is flow through the valvefrom the flow generator;

FIG. 14 is an illustration of the inside view of the valve arrangementof FIG. 13 when there is flow through the valve from the flow generator;

FIGS. 15A and 15B schematically depict a valve arrangement including aplurality of flaps without a flow force and with a flow forcerespectively according to a further example embodiment; and

FIG. 16 illustrates a respiratory treatment system with a rainout valvearrangement having an expandable chamber that is suitable for CPAPtreatment.

DETAILED DESCRIPTION

FIG. 2A schematically depicts a certain embodiment of a respiratorytreatment system. The system includes a positive airway pressure (PAP)or ventilator device 2000 attached to a humidifier 2005. In thisembodiment the humidifier 2005 is integrated with the PAP or ventilatordevice 2000 and may optionally be removably attached. The humidifier2005 may include any type of humidifier, including the respiratoryhumidifier described in co-pending International patent applicationpublication number WO 2010/031126 filed 17 Sep. 2009. Also, anyintegrated PAP device and humidifier arrangements may be used, such asthat described in U.S. Published Patent Application No. 2008/0072900filed 4 May 2005, the contents of both applications are incorporatedherein in their entirety.

The outlet 2012 of the humidifier is coupled to a first end of a rainoutvalve 2100 adapted to open and close the air path between the humidifieroutlet 2012 and an air delivery conduit 2010. The second end of therainout valve 2100 is attached to the device end of air delivery conduit2010. The air delivery conduit 2010 is attached at the patient end to apatient interface 2030. The patient interface or mask may have anysuitable configuration as is known in the art, e.g., full-face mask,nasal mask, oro-nasal mask, mouth mask, nasal prongs, etc. Also,headgear may be utilized to comfortably support the patient interface ina desired position on the patient's face.

Alternatively, the air delivery conduit 2010 may be attached to otherforms of the patient interface such as a nasal cannula 2035 as shown inFIG. 3. Such a system may be used to provide respiratory therapy asdescribed in co-owned and pending International Application PublicationNo. WO 2010/031126, the content of which is incorporated herein in itsentirety. All other forms of patient interface such as a tracheotomytube are also encompassed within the scope of the present technology.

Optionally, a further air delivery conduit may also be provided alongthe air delivery path. For example, as schematically shown in FIG. 2B,the humidifier 2005 may be a separate component from the PAP orventilator device 2000 so that a first air delivery conduit 2010 (1) isplaced between the PAP device 2000 and the humidifier 2005 and a secondair delivery conduit 2010 (2) is placed between the rainout valve 2100and the patient interface 2030. Optionally, an additional rainout valve2100 (not shown) may be coupled to the inlet of the humidifier or theoutlet of the PAP or ventilator device to prevent rainout orcondensation from travelling back through to the PAP or ventilatordevice. Such a rainout valve may also prevent spillback of water intothe flow generator from the humidifier.

FIGS. 4 and 5 depict an example embodiment of a respiratory treatmentsystem with a PAP device 4000 coupled to a humidifier 4005 including arainout valve 4100. The humidifier 4005 may include a removable watertub for ease of filling and cleaning of the water tub as described inU.S. Published Patent Application No. 2008/0072900. The outlet 4012 ofthe humidifier 4005 may be attached to the rainout valve 4100. Therainout valve 4100 is coupled on the opposing end to an air deliveryconduit 4010. The air delivery conduit 4010 is coupled to a nasalcannula 4035 that is attached to headgear 4050 to support the nasalcannula 4035 on a user's face.

In certain embodiments the rainout valve 4100 may include a gas port4200 to allow an optional connection of a supplementary gas, such asoxygen to be provided to the user if desired. The supplementary gassupply may be coupled to a gas connector 4210 using a standard gasconnection.

FIG. 5 is a close up view of the rainout valve 4100 of FIG. 4 attachedto the humidifier outlet 4012. In this embodiment, the rainout valve4100 includes a movable membrane 4110 within an internal channel. Themembrane 4110 is adapted to move, such as by deforming, swinging and/orshifting etc., to open and close the channel to selectively block vaporthrough the internal channel of the rainout valve 4100 depending on thepresence or absence of a pressurized flow from the flow generator. Inthis regard, the internal channel is configured to allow a flow ofhumidified gas to travel from a first side or humidifier side 4102 ofthe rainout valve 4100 to a second side or air delivery conduit side4104 of the rainout valve 4100 when the flow is pressurized by the flowgenerator but to prevent warm vapor from moving from the first side tothe second side when the flow generator is not generating itspressurized flow. Thus, in use the PAP device 4000 generates a supply ofpressurized gas that is delivered to the humidifier 4005 where watervapor is added to the pressurized gas to form a humidified pressurizedgas flow. The humidified pressurized gas flow travels from thehumidifier 4005 to the humidifier outlet 4012 and through to the rainoutvalve internal channel from the first side 4102 pushing the membraneopen (e.g., upwards towards the second side 4104) and then to the airdelivery conduit 4010 and through to the patient interface 4035 toprovide the humidified gas to the user. The direction of the gas flowgenerated by a flow generator of the PAP device 4000 in the system isshown by arrow F in FIG. 5. As previously mentioned, other forms ofpatient interface, such as a mask, nasal prongs, etc. may also beutilized.

Thus, the rainout valve 4100 membrane is adapted to serve as a vaporbarrier to cover or obstruct the internal channel when there is no flowentering the rainout valve from the flow generator. For example, themembrane barrier may be configured to have a default or normally closedposition to close or shut off the internal channel and prevent warmhumidified air from travelling from the first side 4102 to the secondside 4104 of the rainout valve 4100. This can prevent the warmhumidified air from entering any conduit, such as air delivery conduit4010 or other device attached to the second side 4104 of the rainoutvalve 4100 when no flow generator flow is provided, such as when thedevice is switched off after use or between periods of use. Warmhumidified air, if allowed to enter the air delivery conduit 4010, otherconduit or other device, may cool within the conduit or device and formcondensate. The rainout valve 4100 prevents or at least reduces thelevel of condensate formed in the air delivery conduit 4010, otherconduit or device.

In contrast, when the flow generator is operating to provide apressurized flow through the rainout valve, for example, through thehumidifier outlet 4012 from the humidifier 4005 and PAP or ventilatordevice 4000, the membrane 4110 is opened (e.g., pushed upwards towardsthe second side 4104 of the rainout valve 4100) by the gas flow so as toselectively open the vapor barrier. This permits the humidifiedpressurized gas to travel through the internal channel and around themembrane 4110 through to the second side 4104 of the rainout valve 4100.

In such a system, the vapor barrier of the valve may also be configuredto prevent the rebreathing of carbon dioxide if the expired carbondioxide cannot travel back through the system. In this regard, the vaporbarrier or blocking member may also be configured to serve as a backflowpreventer to prevent any back flow from the second side to the firstside (e.g., from the patient interface through to the humidifier and/orflow generator of the PAP device). For example, a higher air pressure atthe second side 4104 (e.g., due to patient expiration) relative to thepressure at the first side 4102 may force or permit the membrane toclose the channel (e.g., such as if the larger membrane plys against asmaller aperture structure of the channel to block the channel asillustrated in FIGS. 6A, 7A and 9A) or may permit the membrane itself toclose to its normal position (such as in the case of the duckbillblocking member illustrated in FIG. 8A). This may occur even when theflow generator is operating. As a result, the flow of expired air may beprevented by the membrane from passing from the second side and enteringinto the humidifier 4005 and/or PAP device 4000. Thus, the expired airis prevented from travelling back to the motor or blower and can preventcontamination or deterioration of these flow generator components bythereby preventing a back flow of any humidified gas and/or anysupplemental gas such as oxygen, to these components. Similarly, theback flow prevention can prevent the expired air and/or supplemental gasfrom entering the humidifier and potentially harming or contaminatingthe components of the humidifier as well. Each of the embodimentsdescribed herein may optionally be configured to serve as such a backflow preventer.

The gas port 4200 may be attached or formed at second side 4104 of therainout valve 4100. A supplementary gas supply such as oxygen, heliox,nitrox, etc. may be attached to the gas port 4200 to supply the userwith a gas, (e.g., oxygen enriched supply of pressurized gas). Thesupplementary gas may be provided from a pressurized source and may becontinuously provided through the gas port 4200. The supplementary gas,(e.g., oxygen) travels up through the air delivery conduit 4010 and thepatient interface 4035 to the user or patient. The supplementary gaswill be delivered to the user or patient during inspiration. When thevalve also serves as a back flow preventer as previously described, thevalve may also help to reduce waste of the supplemental gas. Forexample, during expiration, when the user or patient is exhaling, ahigher pressure may be generated by the patient's exhalation at thepatient interface relative to a lower pressure at the flow generator.This difference in pressure may result in the closing of the membrane inthe channel as previously described when the membrane is configured toserve as a back flow preventer. As a result, the supply of supplementarygas will build up between the rainout valve 4100 and the air deliveryconduit 4010 rather than being vented back out through the humidifierand/or PAP device. Thus, the air delivery conduit 4010 accumulates areservoir of supplementary gas that is ready to be delivered to the useror patient when inspiration commences. Advantageously, this reduces thewastage of supplementary gases during expiration as all or substantiallyall of the supplementary gas is supplied during inspiration.Consequently a lower level of supplementary gas may be required. It isestimated that a reduction in the supplementary gas usage, such asoxygen usage, results in approximately half the standard usage ofsupplementary gas or oxygen. The usage savings and improved efficiencymay result in savings of more than 50% of the standard usagerequirements.

In a further embodiment, the gas port 4200 may be used to provide othersubstances such as medications that may be required by the users. Forexample, asthma medications or other such medications may be applied tothe gas port 4200.

Optionally, gas port 4200, or another similarly situated port, may becoupled to a humidifier bypass tubing or other conduit that is sourcedfrom the flow generator. Such a bypass tubing may be utilized to channela flow of dry air from the flow generator to the patient interfaceconduit at the second side of the rainout valve without passing throughthe humidifier. The flow of dry air through such a humidifier bypasschannel may be generated while the rainout valve is closed and may beutilized to clear out any moist or humidified air that might remain inthe patient interface conduit at the conclusion of a treatment sessionin a shut down procedure. This may help to further reduce rainout.

For example, for such a shut down procedure, a diverter may be activatedto divert the flow generator's flow of breathable gas from traversingthrough the humidifier to instead traverse through the bypass tubing.This would permit the rainout valve to be closed during the shut downprocedure. The diverter may be a simple manual valve or one or more flowcontrol valves that are set by a processor or controller of the PAPdevice. In such a case, the processor may be configured with controlinstructions to control the diverter and flow generator. The processormay perform the shut down procedure by controlling switching of thediverter to the bypass channel and thereafter controlling the blower togenerate the dry flow of air through the bypass channel at thecompletion of a treatment session for a brief period of time (e.g., 30seconds). In some such embodiments, an electro-mechanical valve (e.g., athree port, two way valve) may serve as the diverter. However, otherdevices may be implemented to send the flow to the patient interfaceconduit from the flow generator so as to bypass the humidifier.

In a further embodiment, for constant positive airway pressure (CPAP)therapy where a constant positive airway pressure is required throughoutthe breathing cycle, a system to maintain the constant pressure may berequired. For example, as illustrated in FIG. 16, the rainout valve 2100may include a chamber 1688 having an expandable volume to receive theexpired gas from the patient located on the patient side of the rainoutvalve mechanism (i.e., on the second side 4104 of the rainout valve).Such a chamber may include complaint walls 1699 that allow the expiredgas to expand the chamber and prevent the closure of the valve duringuse, thus maintaining a constant positive pressure. Alternatively, anexhalation valve may be located proximal to the mask to prevent thepressure of the expired gas from shutting the rainout valve.

FIGS. 6A and 6B schematically illustrate a membrane type valve, whichmay be formed by a flexible, resilient material, as shown in theembodiment in FIGS. 4 and 5. FIG. 6A illustrates the rainout valve 4100and membrane 4110 when there is no pressurized flow through an internalchannel 4106 of the rainout valve 4100, for example flow from ahumidifier. The internal channel 4106 is blocked or covered by themembrane 4110 in the relaxed or default position when there is no flowthrough the rainout valve. The membrane may be adapted with a shape tobe generally complementary to the internal channel to block the channel.For example, it may have a slightly larger diameter than the diameter ofthe channel in the event of a cylindrical shaped channel. Alternatively,the membrane may have a bellows type shape such that it may balloon upto deform so as to draw in the sides when gas flow enters the bellows toallow gas flow around the bellows. Still further, other membrane shapesmay be implemented for blocking the internal channel when there is noflow from the flow generator. The membrane 4110 is generally configuredto cover or block the internal channel 4106 to selectively preventvapors or humidified gas to pass from the first side 4102 to the secondside 4104 under certain conditions. The membrane 4110 may be supportedwithin the internal channel 4106 via a support structure 4115. Asdescribed above a supplementary gas port 4200 may optionally be attachedto the second side 4104 of the rainout valve.

FIG. 6B illustrates the rainout valve 4100 and membrane of FIG. 6A whenthere is pressurized flow through the internal channel 4106 of therainout valve (e.g., a higher gas pressure at the first side relative tothe gas pressure of the second side). The pressurized gas flow F entersthe internal channel 4106 from the first side 4102 and pushes themembrane to allow the gas to flow around the membrane and through to thesecond side 4104. The membrane 4110 configured to move or deform at adesired level of flow (e.g., a flow between 4 to 120 L/min). However,the membrane may be implemented to move with other flow rates and maymove proportionally depended upon the level of flow provided. Themembrane 4110 remains open while there is pressurized flow through theinternal channel 4106. When the pressurized flow stops or is turned offthe membrane 4110 will return to the default or relaxed position andblock the internal channel 4106 as illustrated in FIG. 6A.

The above valve arrangements have been described using a membrane typevapor barrier. However, other types of valve systems utilizing otherforms of blocking means or vapor barriers may also be implemented toselectively block the internal channel of the rainout valve. Someadditional example embodiments of the rainout valve are illustrated inFIGS. 7A to 10B and are described in more detail herein.

FIGS. 7A and 7B schematically illustrate another example embodiment of arainout valve 7100 where the blocking member is a flap, such as a hingedflap or a resilient silicone flap, that is configured to close and openaccess through the internal channel 7106 of the rainout valve 7100. FIG.7A illustrates the position of the flap 7120 when there is no flowthrough the system and the flap is in the relaxed or default position.The flap 7120 is configured to have a complementary shape to theinternal channel with a slightly larger size (e.g., diameter). In thisposition the flap 7120 selectively prevents the transport of vapor orhumidified gas from flowing through to the second side 7104 of therainout valve.

FIG. 7B illustrates the action of the flap 7120 when there ispressurized gas flow F through the internal channel 7106. Thepressurized gas flow forces the flap to deform and/or swing to open theinternal channel from the first side 7102 to the second side 7104. Theflap 7120 remains open while there is pressurized flow through theinternal channel 7106. When the pressurized flow stops (e.g., if theflow generator is turned off, if there is an equal gas pressure in thechannel on either side of the flap and/or if a higher gas pressureexists in the channel on the second side relative to the channel gaspressure of the first side, the flap 7120 will return to the defaultposition and block the internal channel 7106 (i.e., the normally closedposition). The rainout valve 7100 may optionally include a supplementarygas port 7200 on the second side 7104 of the rainout valve adapted toreceive a supply of supplementary gas.

FIGS. 8A and 8B schematically illustrate another example embodiment of arainout valve 8100 where the blocking member or vapor barrier has aduckbill arrangement 8130. FIG. 8A illustrates the duckbill arrangement8130 when there is no flow through the system and the duckbillarrangement 8130 is in the relaxed or default position. In the relaxedor normally closed position the duckbill arrangement 8130 has a duckbeak like end 8135 such that two sides of the beak type end 8135 areresiliently and coextensively aligned together to form a seal or vaporbarrier to prevent the transport of vapor or humidified gas from thefirst side 8102 through to the second side 8104 of the rainout valve8100. The opposing end 8132 of the duckbill arrangement 8130 has agenerally tubular or cylindrical opening. The opposing end 8132 mayoptionally be inserted over an end of a tube outlet such as a humidifieroutlet and no further valve housing structure maybe required (notshown). The duckbill valve may be manufactured from an elastomericmaterial such as rubber.

FIG. 8B illustrates the action of the duckbill arrangement 8130 when theflow generator generates the pressurized gas flow F through the opposingend 8132 to the beak type end 8135 of the duckbill arrangement 8130. Thepressurized gas flow forces the two sides of the beak type end 8135 todeform outwards to open the duck beak and then enters the internalchannel from the first side 8102 to the second side 8104. The duckbillarrangement 8130 remains open while there is pressurized flow throughthe internal channel 8106. When this pressurized flow stops (e.g., theflow generator is turned off), the two sides of the beak type end 8135will return to the default position and block the internal channel 8106.The rainout valve 8100 may optionally include a supplementary gas port8200 on the second side 8104 of the rainout valve adapted to receive asupply of supplementary gas.

FIGS. 9A and 9B schematically illustrate another example embodiment of arainout valve 9100 where the vapor barrier or blocking member 9140 iscontrolled by a biasing member such as a spring 9145. The spring may beattached or incorporated with the blocking member 9140 and a supportstructure 9142 fixed within the internal channel 9106. The blockingmember 9140 may be made from any lightweight material, such as a thinplastic disc, and is adapted to block or close off access through theinternal channel 9106 of the rainout valve 9100 when there is nopressurized flow therethrough. The blocking member 9140 may beconfigured to have a complementary shape to the internal channel (e.g.,with a slightly larger diameter). However, it is appreciated that otherblocking member shapes may be used. FIG. 9A illustrates the biasingmember providing a biasing force to normally close the vapor barrier ofthe valve. For example, the spring 9145 in a relaxed or relativelyuncompressed state maintains the blocking member in a sealed positionwhen there is no flow through the system. Under this condition, theblocking member 9140 is selectively located in a position to seal orblock the internal channel 9106. Thus, the blocking member 9140 may alsobe in a relaxed or default position. In this position the blockingmember 9140 prevents the transport or vapor or humidified gas fromflowing through from the first side 9102 to the second side 9104 of therainout valve 9100.

FIG. 9B illustrates the action of the biasing member such as the spring9145 and blocking member 9140 when there is pressurized gas flow Fthrough the internal channel 9106. The pressurized gas flow pushes theblocking member 9140 to shift the blocking member (e.g., upwards) andcompresses the spring 9145 to open the internal channel from the firstside 9102 to the second side 9104 allowing the pressurized gas to flowthrough the internal channel 9106. The blocking member 9140 remains openwith the spring 9145 compressed while there is pressurized flow throughthe internal channel 9106. When the pressurized flow stops or is turnedoff the blocking member 9140 is no longer forced upwards and the spring9145 returns the blocking member 9140 to the normally closed position toblock the internal channel 9106. The rainout valve 9100 may optionallyinclude a supplementary gas port 9200 on the second side 9104 of therainout valve adapted to receive a supply of supplementary gas.

Although the resilient biasing member in this embodiment is configuredto compress as a result of a flow from the flow generator, in analternative embodiment, the biasing member may be configured on theopposite side of the blocking member from that illustrated in FIGS. 9Aand 9B such that movement of the blocking member as a result of the flowstretches the resilient biasing member. In the absence of flow thebiasing member is configured to recoil or contract to its normal ordefault position to block the passage from the first side 9102 to thesecond side 9104. Thus the biasing force from the recoiling orcontracting applied to the blocking member will then move the blockingmember to again seal the channel to reduce vapor transfer through thechannel.

FIGS. 10A and 10B schematically illustrate another example embodiment ofa rainout valve 100 having a blocking member 150, such as one or moreflaps or hinged flaps. In this embodiment the rainout valve 100 includesan internal channel 106 to transport the supply of pressurized gas froma first side 102 to a second side 104. The blocking member or flap isadapted to block the passage through the internal channel 106 from thefirst side 102 to the second side 104 in the default (normal) or relaxedposition as shown in FIG. 10A. An aperture 160 to atmosphere is providedon a surface on the second side 104 of the rainout valve 100. The flapis attached or hinged at a junction 155 between the aperture 160 and theblocking region of the internal channel 106. The flap is adapted topivot and/or flex to move between a first position and a secondposition. The first position may be a default or relaxed position whenthere is no pressurized flow through the internal channel from the flowgenerator. In this first default or relaxed position the flap blocks theaccess through the internal channel 106 from the first side. However,the aperture 160 is open to atmosphere as shown in FIG. 10A for accessto the channel at the second side. Having the second side 104 of therainout valve open to atmosphere in this way allows any humidified gaspresent in the second side 104 or in the air delivery conduit or deviceattached to the second end 104 of the rainout valve to be vented toatmosphere. This may allow the second side 104 that is attached to theair delivery conduit or patient interface to dry. This is particularlyuseful after a treatment session with the respiratory treatmentapparatus when a supply of humidified gas has been provided through thesystem. The remaining warm moist gas may escape through the aperture 160to atmosphere rather than being trapped and allowed to condense withinthe attached air delivery conduit or other attached device.

In contrast, as seen in FIG. 10B, when the flap is forced or pivoted tothe second position, such as by the pressurized gas flow F, to unblockor open the internal channel 106 from the first side 102 to the secondside 104, and to substantially simultaneously close or block theaperture 160 and prevent the escape of pressurized gas to atmospherethrough the aperture 160. In this way, the blocking member or vaporbarrier is operable to selectively permit or prevent vapor from enteringthe channel from the first end that may be associated with a humidifieroutput, and to selectively permit or prevent vapor from exiting thechannel to atmosphere.

In these embodiments, the blocking member 150 is illustrated as a flapbut may be implemented by any other form of valve arrangement.Optionally in another embodiment the aperture 160 may be adapted to beremovably plugged with an adaptor configured to allow the connection ofa supplementary gas supply when required instead of being used as anaperture to atmosphere in a similar manner to the embodiments describedabove. It may be desirable to block the vent to atmosphere when using asupplementary gas source as this may result in wastage of thesupplementary gas.

FIGS. 11 to 14 are illustrations of a further example embodiment of arainout valve including a vent or aperture to atmosphere similar to thatdescribed in relation to FIGS. 10A and 10B. FIGS. 11 and 12 show ablocking member 150 or vapor barrier in a relaxed or default (normal)position from an outside view and inside view respectively. In thisversion, the vapor barrier may be formed by a flap that is operable toselectively block the internal channel between the first side 102 andthe second side 104. The aperture 160 is shown open to atmosphere.

FIGS. 13 and 14 show the position of the flap when a force is suppliedby the pressurized gas flow in the internal channel 106 and to the flapfrom an outside view and inside view respectively. The flap is openedwithin the internal channel 106 to provide access therethrough from thefirst side 102 to the second side 104. The flap is forced to cover orblock the aperture 160 and consequently block any venting to atmospherethrough the aperture 160.

FIGS. 15a and 15b show a further embodiment based on a similararrangement to that shown in FIGS. 7A and 7B but with a plurality ofhinged flaps, such as two hinged flaps. In such an arrangement each flapis moved to block one or more apertures 7160 a, 7160 b that vent toatmosphere when a force or pressure is applied by the gas flow throughthe aperture from the first side 7102 to the second side 7104. One ormore apertures 7160 a, 7160 b to atmosphere are located in the extendedarms of the valve 7100.

FIG. 15A illustrates the position of the flaps 7120 a, 7120 b when thereis no flow through the system and the flaps are in the relaxed ordefault positions. The flaps 7120 a, 7120 b are configured to overlap toobstruct the internal channel. In this position the flaps 7120 a, 7120 bselectively prevent the transport of vapor or humidified gas fromflowing through to the second side 7104 of the rainout valve. In thisarrangement one or more apertures 7160 a, 7160 b that vent to atmosphereare unobstructed to allow air from atmosphere to pass into the secondside of the 7104 of the rainout valve. In a similar manner to thatdescribed in relation to FIG. 10a above.

FIG. 15B illustrates the action of the flaps 7120 a, 7120 b when thereis pressurized gas flow F through the internal channel 7106. Thepressurized gas flow forces the flaps to deform and/or swing to open theinternal channel from the first side 7102 to the second side 7104 andsimultaneously block or obstruct the one or more apertures 7160 a, 7160b that vent to atmosphere to prevent gas from exiting via theseapertures 7160 a, 7160 b. The flaps 7120 a and 7120 b continue toprovide an open internal channel 7106 and blocked apertures 7160 a, 7160b to atmosphere while there is pressurized flow through the internalchannel from the flow generator. When the pressurized flow stops (e.g.,if the flow generator is turned off, if there is an equal gas pressurein the channel on either side of the flap and/or if a higher gaspressure exists in the channel on the second side relative to thechannel gas pressure of the first side, the flaps 7120 a, 7120 b willreturn to their default positions and block the internal channel 7106and open the apertures 7160 a, 7160 b to atmosphere (i.e., the normallyclosed position).

It is noted that other arrangements may be utilized that move anobstruction component from a first position to a second position basedon the absence or presence of pressurized gas flow through the rainoutvalve. Wherein in the first position the obstruction component isconfigured to block the passage from a first side of the rainout valveto a second side of the rainout valve while allowing venting toatmosphere. In the second position the obstruction component isconfigured to block the venting to atmosphere while allowing the passageof flow from a first side of the rainout valve to a second side of therainout valve. Such mechanisms are encompassed within the scope of thepresent technology.

The blocking members illustrated in FIGS. 6A to 10B, 15A and 15B areshown as being located in a substantially central location of therainout valve internal channels. However, it is appreciated that theblocking members may be located anywhere within the internal channel toblock the transport of vapor or humidified gas flow from exiting thesecond side of the rainout valve.

In the above embodiments the rainout valve 100, 2100, 4100, 7100, 8100,9100 is illustrated as an separate component connectable with andbetween the humidifier outlet 2012 and the air delivery conduit 2010,2010 (2), for example, by a coupling or other connector. In this way,the valve may be used with many different types of respiratory treatmentapparatus. However, it should also be appreciated that the rainout valvemay be an integrated component of the outlet 2012 of the humidifier2005. Alternatively, the rainout valve may be integrated into the deviceend of the air delivery tube 2010, 2010 (2).

The rainout valves as described above are passive pneumaticallycontrolled rainout valves. However, it is to be appreciated thatactively controlled valves such as electrically controlled,piezo-controlled, electromagnetic controlled or other such activelycontrolled valves may also be utilized. For example the activeelectromagnetically controlled valve described in International patentapplication PCT/AU2010/000708 filed 9 Jun. 2010, the contents of whichis incorporated herein in its entirety, may be used. This active valvemay be used to control the flow of warm humidified air through ahumidifier system as described in the application.

Furthermore, any form of blocking means or vapor barrier configured toselectively shut off or block the transfer path from the outlet of ahumidifier is encompassed within the scope of the present technology.For example, shutter systems may be employed. Furthermore, the blockingmeans, such as when integrated into a humidifier outlet or into andelivery conduit, may be designed in a manner to allow humidified gas toflow through the blocking means or valve during pressurized flowgeneration but to prevent water from spilling into the conduit. Thisadvantageously would also prevent users from filling humidifier tube viathe deliver conduit and consequently reduce the risk of overfilling thehumidifier water tub.

In some embodiments, the vapor barrier may be configured so as not toprevent pressure detection across the medium of the closed barrier.Rather, it may be configured to permit a detection of pressure changesfrom one side of the vapor barrier that exist on the opposing side ofthe vapor barrier. Thus, the vapor barrier may effectively transmit thepressure changes through its medium such as by vibrating or by itspliability while it remains in a closed, vapor blocking position. Forexample, while the vapor barrier is closed, its pliability may allow itto expand/compress or otherwise respond to pressure changes at thepatient interface side of the vapor barrier. In the case of an increasein pressure in the patient interface that may be attributable to patientexpiration on the second side of the membrane, the increase in pressuremay cause the membrane to expand into an area associated with the firstside of the membrane (e.g., towards the flow generator and humidifier)while still preventing back flow through the rainout valve. Thisexpansion of the vapor barrier may effectively compress the air on thefirst side of the vapor barrier proportionally to the compression of airon the second side of the vapor barrier. A pressure sensor located inthe flow generator and/or humidifier may then be able to detect thischange in pressure on the first side of the vapor barrier. Similarly, asubsequent decrease in pressure at the patient interface end (e.g.,patient inhalation) may permit the membrane of the vapor barrier torelax (even before it opens) so as to reduce the pressure at the firstside of the vapor barrier proportionally to the reduction on the secondside proximate to the patient interface.

Accordingly, even when the vapor barrier acts as a back flow preventer,it may be configured to allow sensing of pressure changes attributableto the patient interface side without using a pressure sensor at thepatient interface side. That is, a pressure sensor may still beimplemented by the PAP device at the flow generator or humidifier sideof the vapor barrier and effectively detect pressure changes through theclosed barrier. This may be useful for different control routines thatmay be implemented by a processor or controller of the PAP device thatare based on pressure detection. For example, the processor may detectan increase in pressure through the vapor barrier as a trigger forstarting the flow generator as part of a SmartStart feature. Such aSmartStart procedure is described in U.S. Pat. No. 6,240,921, thedisclosure of which is incorporated herein by reference. Similarly, theprocessor may detect a reflected oscillating pressure waveform (e.g., 4Hz) originally generated by the flow generator that is reflected backfrom the patient such that it vibrates the closed vapor barrier at avelocity proportional to the reflected pressure waveform. This processmay allow the controller to thereby detect an open patient airwaythrough the closed vapor barrier. Such an open airway detection processis described in U.S. Pat. No. 5,704,345, the disclosure of which isincorporated herein by reference.

In the foregoing description and in the accompanying drawings, specificterminology, values and drawing symbols are set forth to provide athorough understanding of the present technology. In some instances, theterminology and symbols may imply specific details that are not requiredto practice the technology. For example, although the terms “first” and“second” have been used, unless otherwise specified, they are notintended to indicate any order but may be utilized to distinguishbetween distinct elements of the technology.

In this specification, the word “comprising” is to be understood in its“open” sense, that is, in the sense of “including”, and thus not limitedto its “closed” sense, that is the sense of “consisting only of”. Acorresponding meaning is to be attributed to the corresponding words“comprise,” “comprised” and “comprises” where they appear. It is furtherto be understood that the word “humidifier outlet” in this specificationrefers to any outlet from a humidifier including a water tub outlet orto an outlet to which a conduit is attached.

It will further be understood that any reference herein to known priorart does not, unless the contrary indication appears, constitute anadmission that such prior art is commonly known by those skilled in theart to which the present technology relates.

Although the technology has been herein shown and described in relationto humidified respiratory apparatuses and systems it is to be understoodthat any humidifier system or vapor generation system may utilize such arainout valve arrangement. The rainout valve arrangement may be coupledor attached between any such humidifier or vapor generation system and aconduit or other device in which the presence of condensate or rainoutin the conduit or other device would be undesirable. Furthermore, whilethe humidifier respiratory system described are what is conceived to bethe most practical and preferred embodiments, it is recognized thatdepartures can be made within the scope of the technology, which is notto be limited to the details described herein but is to embrace any andall equivalent assemblies, devices and apparatus.

The invention claimed is:
 1. A device to reduce conduit rainout, thedevice comprising: a gas conduit having an input aperture and an outputaperture, the gas conduit configured as a channel for movement of abreathable gas between the input aperture and the output aperture,wherein the gas conduit is configured to provide the breathable gas fromthe output aperture to a patient interface; a pressure responsive vaporbarrier operable to selectively prevent vapor passing from the patientinterface through the gas conduit to the input aperture; and a bypassconduit configured to channel a flow of dry air from a flow generator ofa respiratory treatment apparatus to the gas conduit at a patientinterface side of the vapor barrier when the vapor barrier selectivelyprevents vapor passing from the patient interface through the gasconduit to the input aperture.
 2. The device of claim 1, wherein thevapor barrier is configured to normally seal the channel to preventvapor passing from the output aperture to the input aperture.
 3. Thedevice of claim 2, wherein the vapor barrier is configured to open topermit the breathable gas to pass from the input aperture to the outputaperture by an application of pneumatic pressure applied at the inputaperture that exceeds the pressure at the output aperture.
 4. The deviceof claim 3, wherein the vapor barrier is configured to close to preventvapor passing from the output aperture to the input aperture with apneumatic pressure applied at the output aperture that exceeds or isequal to pressure at the input aperture.
 5. The device of claim 4,wherein the vapor barrier comprises a valve flap.
 6. The device of claim5, wherein the valve flap is formed of a flexibly resilient material. 7.The device of claim 4, wherein the vapor barrier comprises an aperturecover and biasing member.
 8. The device of claim 1, wherein the gasconduit is configured at the output aperture as a coupling for thepatient interface.
 9. The device of claim 1, further comprising: apositive airway pressure device; and a humidifier, wherein thehumidifier is coupled to the positive airway pressure device and theinput aperture of the gas conduit.
 10. The device of claim 1, whereinthe device is an attachment at an outlet of a humidifier.
 11. The deviceof claim 1, wherein the vapor barrier is configured for a detection ofpressure changes from one side of the vapor barrier that exist on anopposing side of the vapor barrier when the vapor barrier is closed toprevent vapor passing from the output aperture to the input aperture.12. The device of claim 1, wherein the gas conduit further comprises anatmosphere access port.
 13. The device of claim 12 wherein the vaporbarrier is further configured to cover the atmosphere access port whenthe vapor barrier permits the breathable gas to pass from the inputaperture to the output aperture.
 14. The device of claim 12, wherein thevapor barrier is further configured to uncover the atmosphere accessport when the vapor barrier prevents vapor passing from the outputaperture to the input aperture.
 15. The device of claim 12, wherein thegas conduit is configured at the output aperture as a coupling for thepatient interface.
 16. The device of claim 12, wherein the vapor barriercomprises a bellows.
 17. The device of claim 12, wherein the vaporbarrier comprises a duckbill valve.
 18. The device of claim 12, whereinthe gas conduit is configured at the input aperture as a coupling for ahumidifier.
 19. A device to reduce conduit rainout, the devicecomprising: a gas conduit having an input aperture and an outputaperture, the gas conduit configured as a channel for movement of abreathable gas between the input aperture and the output aperture,wherein the gas conduit is configured to provide the breathable gas fromthe output aperture to a patient interface; a vapor barrier operable toselectively prevent vapor passing from the patient interface through thegas conduit to the input aperture; a pressure sensor located upstream ofthe vapor barrier; wherein the vapor barrier is configured to normallyseal the channel to prevent vapor passing from the output aperture tothe input aperture; wherein the vapor barrier is configured to open topermit the breathable gas to pass from the input aperture to the outputaperture by an application of pneumatic pressure applied at the inputaperture that exceeds the pressure at the output aperture; wherein thevapor barrier is configured to close to prevent vapor passing from theoutput aperture to the input aperture with a pneumatic pressure appliedat the output aperture that exceeds or is equal to pressure at the inputaperture; and wherein the vapor barrier is configured to transmitpressure changes that occur on a downstream side of the vapor barrier,through the vapor barrier, such that the pressure changes are detectedby the pressure sensor when the vapor barrier is closed.
 20. The deviceof claim 19, wherein the gas conduit further comprises an atmosphereaccess port, and wherein the vapor barrier is further configured tocover the atmosphere access port when the vapor barrier permits thebreathable gas to pass from the input aperture to the output aperture.21. The device of claim 20, wherein the vapor barrier is furtherconfigured to uncover the atmosphere access port when the vapor barrierprevents vapor passing from the output aperture to the input aperture.22. A respiratory treatment apparatus having: means for reducing conduitrainout within a gas conduit of the respiratory treatment apparatus,wherein the means for reducing conduit rainout is configured forselectively preventing vapor passing from a patient interface throughthe gas conduit to an input aperture of the gas conduit; means forsensing pressure, the means for sensing pressure located upstream of thevapor barrier; and means for conducting a breathable gas between theinput aperture and an output aperture of the gas conduit; wherein themeans for reducing conduit rainout is configured to transmit pressurechanges that occur on a downstream side of the means for reducingconduit rainout, through the means for reducing conduit rainout, suchthat the pressure changes are detected by the means for sensing pressurewhen the means for reducing conduit rainout is closed.
 23. Therespiratory treatment apparatus of claim 22, wherein the means forreducing conduit rainout within the gas conduit is also a means fornormally sealing the gas conduit to prevent vapor passing from an outputaperture of the gas conduit to the input aperture.
 24. The respiratorytreatment apparatus of claim 23, wherein the means for reducing conduitrainout within the gas conduit is also a means for permitting abreathable gas to pass from the input aperture to the output aperture byan application of pneumatic pressure applied at the input aperture thatexceeds the pressure at the output aperture.
 25. The respiratorytreatment apparatus of claim 22, wherein the means for reducing conduitrainout within the gas conduit is also a means for allowing vapor topass from the patient interface to atmosphere.